JPH0632380B2 - Method for manufacturing multilayer wiring board - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer wiring board used for high-performance, high-performance and high-density mounting of IC, LSI or small passive components.

2. Description of the Related Art In recent years, demands for miniaturization and multi-functionalization of devices have been increasing year by year. On the other hand, there are great advances in the technology of high-speed signal processing. Under such circumstances, multilayer wiring board technology using ceramics is in an important position as a board for high-density mounting of small devices and a board for high-speed device mounting. Conventionally, there are roughly two types of ceramic multilayer wiring board technologies (for example, Electronic Technology, Vol. 24, No. 4, P 26 to 30).

One of them is to print a tungsten or molybdenum paste on a green sheet consisting of an inorganic component whose main component is alumina powder, an organic binder, and a plasticizer. Alternatively, a method in which a tungsten or molybdenum paste and an alumina paste are sequentially printed and integrated on an alumina green sheet and sintered at a high temperature in a reducing atmosphere. In the multilayer substrate obtained by this method, it is customary to plate the surface layer portion of tungsten or molybdenum metal with gold or the like in order to prevent corrosion and enable soldering. The other method, which should also be called thick-film printing, is used to print conductor paste (Au, Ag) on a sintered alumina substrate.
/ Pd, Cu, etc.) and glass paste are printed for each layer,
This is a method of repeating drying and firing. Of this method, A
The conductors of u and Ag / Pd are fired at 850 to 900 ° C. in air, and Cu is fired at 850 to 900 ° C. in a nitrogen atmosphere.

Problems to be Solved by the Invention However, of the two methods described above, the green sheet method uses alumina as an insulating material, and thus has the advantage of being excellent in insulating characteristics and thermal conductivity and capable of increasing the number of stacked layers. Since tungsten or molybdenum is used as the conductor material, there is a disadvantage that the conductor resistance of the wiring portion is high (5 to 10 times that of Cu), and the cost is high in that the surface conductor layer must be plated with gold. Further, in this method, there is a drawback that the pattern accuracy of the wiring cannot be sufficient because the dimensions after firing are varied due to firing of the unfired integrated body.

On the other hand, the thick film printing method is advantageous as a substrate for high-speed signal processing because it can use materials with sufficiently low conductor resistance, such as Au and Cu, and it will be stacked on a sintered substrate. Therefore, there is an advantage that the dimensional accuracy is sufficient.
However, in this method, it is necessary to perform printing, drying, and firing layer by layer in order to form the conductor and the insulating layer, which complicates the process and deteriorates the insulating layer with each firing, resulting in insufficient insulation characteristics. However, there is a drawback in that the yield is reduced. Among these methods, the method using Au is extremely expensive, and it is strongly desired to use Cu, which is a low cost and low conductor resistance material.

In view of the above problems, the present invention provides a method for manufacturing a multi-layer wiring board including both low cost, low resistance copper wiring and tungsten wiring layers, which has the advantages of both the green sheet method and the thick film printing method. is there.

Means for Solving the Problems In order to solve the above problems, the method for manufacturing a multilayer wiring board according to the present invention includes a small hole in the uppermost insulating layer of a laminated integral sintered body made of alumina and tungsten or molybdenum. , Pt
Or a step of filling a paste consisting of Pd or a mixed powder of these and a low melting point glass that does not oxidize tungsten or molybdenum and alumina powder, and heat treating to densify the filling, and a copper oxide paste and glass or this on top of this. Repeatedly printing mixed powder paste of ceramics and ceramics,
It comprises a step of drying, a step of heat treating this in air to remove the binder, a step of heat treating in a reducing atmosphere to copper metal copper oxide, followed by firing and densification.

Operation The present invention makes it possible to manufacture the multilayer wiring board of the present invention by the above-mentioned processes and the following reasons and actions.

According to the present invention, copper oxide is used as a starting material for forming the low resistance copper wiring layer. The reason for using this copper oxide is that the raw material is prepared in the form of paste because the copper oxide layer and the insulating layer laminated therewith are required to be printed, and the paste contains a large amount of organic binder. If the organic binder remains in the film in the form of carbon or the like during the densification process, it causes pinholes and bubbles, and it is desirable to completely remove it. Therefore, in the present invention, copper oxide is used as the starting material for the copper conductor layer, and the organic binder is completely calcined in air, then reduced, and further densified. When a copper metal powder raw material is used as the conductor material, it is necessary to remove the binder in an atmosphere containing no oxygen such as a nitrogen atmosphere. Therefore, a small amount of the binder remains in the film, which deteriorates the insulating property. Since the copper multi-layered part of the present invention takes the above steps, the insulating layer is extremely densified and exhibits excellent insulating properties. On the other hand, tungsten or molybdenum is used as the conductor material of the internal laminated body portion. These materials are extremely stable in a reducing atmosphere, but have a property that when they come into contact with air, oxidation rapidly proceeds from a temperature of about 400 ° C. to 500 ° C. and disappears as a volatile gas. Therefore, when the treatment in air is required to form the copper multilayer portion as in the present invention, the internal tungsten or molybdenum conductor layer is oxidized and cannot be used as a conductor. In the present invention, one of the important points is that the internal tungsten or molybdenum layer has a structure that can withstand such heat treatment in air. As a means for this, in the present invention, platinum (Pt) or palladium (Pd) is used.
Alternatively, a paste obtained by kneading a mixture of these and a low melting point glass powder made of a component that does not oxidize tungsten or molybdenum, an alumina powder and an organic vehicle is filled, and heat treatment is performed in air or a nitrogen atmosphere to densify. . The purpose of this is to electrically connect the uppermost layer and the inner layer portion with respect to the inner layer containing tungsten or molybdenum and to prevent the inner layer portion from being oxidized even after the heat treatment in air. In the densified packing material, Pt or Pd or a mixture thereof acts as a conductor, and the glass and alumina function to prevent oxygen from penetrating inside. The heat treatment for densifying this filling machine can be performed in air, but this is because the low-melting glass begins to flow and coats the surface before tungsten or molybdenum starts to oxidize in the process of heating, so that it does not react with external oxygen. This is because the reaction of does not proceed. Further, it is desirable that the glass does not contain a component such as lead oxide (PbO). This is because if a component that is easily reduced, such as lead oxide, is included, tungsten or molybdenum is easily oxidized by this, and conductivity is lost.

As described above, according to the present invention, the filling machine is formed in the alumina fired substrate uppermost layer small hole portion having the tungsten or molybdenum inner layer, and after the heat treatment in the air does not oxidize the inside, the copper oxide paste is added. Alternately printing and drying glass powder or a mixture paste of this and ceramic powder, and then removing the binder in the air all at once,
Further, by taking a step of densifying in a reducing atmosphere, it is possible to integrate the alumina-tungsten or molybdenum-based multilayer structure with the copper-glass or glass-ceramics-based multilayer structure.

The composition of the filler is 60 to 90 w% as a conductor component.
It is desirable to be in the range of. This is because if it is less than 60 w%, the conductivity cannot be sufficiently obtained, and if it is 90 w% or more, it becomes impossible to completely prevent the invasion of oxygen into the inside.

Examples Examples are shown below.

Example 1 An insulating layer of 92 w% alumina containing a sintering aid component such as silica and magnesia and a tungsten conductor layer were formed, and a plurality of minute portions (0.3 mm square) of the inner conductor layer were exposed at the uppermost portion. A laminated sintered body on which an insulating layer having such small holes was formed was prepared. This is a laminate obtained by alternately printing and drying a tungsten paste and an alumina paste on an alumina green sheet and firing the laminate at 1580 ° C. in a wet nitrogen-hydrogen mixed atmosphere. The small pores of this laminated sintered body were screen-printed with pastes of the components shown in Table I, dried in air at 100 ° C. for 10 minutes, and then baked in a thick film vector at 850 ° C. in air for 30 minutes.

The glass components shown in Table I soften at about 450 ° C.

A paste obtained by kneading copper oxide powder and tempinate oil dissolving 10 w% ethyl cellulose so as to come into contact with the filling machine was screen-printed and dried on the upper part of the fired body, and then the components shown in Table II were further added. A paste obtained by kneading the glass powder-ceramic powder mixture consisting of the above and the above ethylcellulose-terepinol vehicle was screen-printed and dried.

The printing of the insulating layer paste was performed twice. The above steps were repeated so that the copper oxide layer became the uppermost layer, and printing was performed such that the copper oxide layer including this uppermost layer became three layers. In the steps so far, a screen printing plate designed to connect the inner tungsten layer and the outer copper oxide layer with each interlayer via was used. This printed laminate was treated in air at 800 ° C. for 15 minutes, and then a mixed atmosphere of H ₂ / N ₂ = 10/90, 45
Treat at 0 ° C for 15 minutes, then raise the temperature to 1 in pure N _2.
After holding at 030 ° C. for 30 minutes, it was cooled and taken out from the furnace.

The fired substrate was sintered as a dense structure, the wiring resistance of the copper multilayer portion was 2 to 3 mΩ / port, and the interlayer insulation resistance of the copper conductor was 0.5 × 1 × 10 ¹³ Ω. The resistance of the tungsten conductor layer was about 15 mΩ / port.
Also, the resistance connecting the internal tungsten and the copper metallization layer was extremely low, and accurate evaluation was difficult, but the resistance value was the smallest when the amount of metal (Pt) was 75 w%, 60 w%, 9 w
At 0 w%, the values were about 15 to 20% higher than those of 75 w%.

However, this value is so small as not to cause any problem in practical use. Also, when the inner layer portion was molybdenum, the same degree as that of tungsten was obtained, and even when molybdenum was used for the inner layer conductor, the same effect as tungsten was obtained.

As described above, according to the present invention, the alumina-tungsten or molybdenum-based multilayer sintered body is formed with a filler made of Pt or Pd, a low melting point glass and alumina, and is insulated from the copper oxide paste. After printing the paste alternately and repeatedly, heat treatment in air and reduction atmosphere treatment,
By carrying out the densification treatment all at once, a composite multilayer structure of alumina-tungsten or molybdenum system and glass or this and ceramic mixture-copper system is obtained.

As a result, it is possible to combine an advanced multi-layer method and a multi-layer substrate with excellent thermal conductivity with a multi-layer substrate with extremely low wiring resistance. It is also suitable for mounting parts that require high accuracy.

Claims (1)

[Claims] 1. A small hole portion of a sintered body in which a small hole is provided in the uppermost insulating layer of a laminate composed of an insulating layer containing alumina as a main component and a tungsten or molybdenum metal conductor layer so that the internal conductor is exposed. A paste composed of 60 to 90 w% of platinum powder, palladium powder or a mixture thereof and 40 to 10 w% of a frit component composed of a low melting point glass powder composed of a component that does not oxidize tungsten or molybdenum and an alumina powder and an organic vehicle. Filling step, firing the laminated body in air or N ₂ to densify the filled portion, printing paste with copper oxide powder and organic vehicle on it, and at a temperature lower than the melting point of copper. A step of repeating a step of printing and drying a paste consisting of glass powder to be sintered or a mixed powder of this and ceramic powder and an organic vehicle; A step of heat-treating this in air to remove the binder, a step of heat-treating this in a reducing atmosphere to reduce copper oxide to copper metal, and a step of heat-treating this in a neutral atmosphere or a reducing atmosphere to remove copper and oxides. A method for manufacturing a multilayer wiring board, which comprises a step of sintering and densifying an insulating layer.